For the agrochemical compositions of the invention, the alkylpolysiloxanes of high silicone character (HSCAS) contained therein are defined herein as having blocks of unmodified polydimethylsiloxane segments in their molecular structure, i.e. at least 10 uninterrupted D groups (-Me2SiO—) on average, and having hydrocarbon radicals providing good compatibility with the oil.
The HSCAS reduce the surface tension of the agricultural spray oils and improve the spread coverage on foliage, including those leaves with hydrophobic surfaces and/or corrugated surfaces or those which are positioned other than horizontally, thereby enhancing the performance of the agrochemical compositions. However, the state of the art had not taught the use of HSCAS in agrochemical compositions.
In 1993, Stevens prepared the first extensive review on the use of “Organosilicone Surfactants as Adjuvants for Agrochemicals.” It was suggested that oil spreading for insect control and improved foliage coverage might be enhanced by organosilicones, but no studies were referenced nor were any oils cited. Pesticide Science, pp. 103-122, 1993(38).
Policello et al. reported the use of low molecular weight alkyloligosiloxanes as additives for spray oil applications with vegetable and mineral oils (see Policello et al., Alkylsilicones for Agricultural Oils and Oil-Based Formulations, Fourth International Symposium on Adjuvants for Agrochemicals, Melbourne, Australia, 3-6 Oct. 1995, FRI Bulletin No. 193), pgs 303-307.) However, the alkyloligosiloxanes described therein were of low molecular weight (350-500 g/mol) with short silicone chains such as trisiloxanes, which are known to be key structural elements of silicone polyethers effective as adjuvants for aqueous spreading, whereas higher siloxane chains are generally known in the art to be less effective for spreading of aqueous compositions. Also, the described alkyloligosiloxanes do not have high silicone character.
Gaskin et al. reported the effect of unspecified alkylsiloxanes for improved spreading and efficacy of oil-based insecticidal sprays (Gaskin et al., Enhancement of plant and petroleum-derived spray oils with alkylsilicone surfactants, Spray Oils—Beyond 2000, pgs. 56-61, University of Western Sydney (2002). However, the alkylsiloxanes required relatively high use rates; further more no indication was there that the special effects of HSCAS were considered or investigated.
Murphy et al. (U.S. Pat. No. 5,561,099) refer to increasing the spreading properties of oil-containing compositions by adding to the composition a linear alkylsilicone of the formula:(CH3)3Si—O—(Si(CH3)2O)x—Si(CH3)(R)O)y—Si(CH3)3 
or a cyclic alkylsilicone compound:

where x is an integer from 0 to 20, y is an integer from 1 to 10, m is an integer from 0 to 4, n is from 1 to 5 provided that m-f-n is from 3 to 5, and R is an alkyl group. These alkylsilicone compounds are used as adjuvants in preparing agricultural formulations which contain mineral or vegetable oils.
However, the compounds specified in detail are low molecular weight siloxanes with a low silicone character and as such not optimized for mineral oil-containing sprays.
U.S. Pat. No. 5,658,851, discloses lipophilic siloxanes which decrease the surface tension of oils. These siloxanes have the following general formula:RaMe(3-a)Si{OSiMe2}x—{OSiMeR}y—OSiMe(3-a)Ra where R is a lipophilic group selected from the group consisting of aryl, substituted aryl, aralkyl, alkyl phenyl ether, substituted phenylether, or alkyl alkyleneoxide groups; a is 0 or 1; x and y is 0 to 4 depending upon a, provided that the sum of x and y is greater than or equal to 6. Those siloxanes are referred to be adjuvants in oil-based herbicidal, disease treatment, or insecticidal compositions.
However, again the compounds described are low molecular weight siloxanes with a low silicone character which are not optimized for mineral oil containing sprays.
Finally, Murphy et al. (U.S. Pat. No. 5,658,852) disclose that one can increase the spreading properties of oil-containing pesticidal compositions by adding to the composition a linear alkylsilicone of the formula:(CH3)3Si—O—(Si(CH3)2)O)x—(Si(CH3)(R)O)y—Si(CH3)3 wherein x=0 to 20, y=1 to 10 and R and alkyl or alkyl ester group containing 6 to 18 carbons.
However, this as well as the previous patents does not recognize the benefit of alkylpolysiloxanes with high silicone character in mineral oil-containing formulations; the siloxanes referred to in Murphy are only effective in relatively high consumption rates, and do not perform well with mineral oils.
Kennedy et al. (U.S. Pat. No. 6,669,949) refers to asymmetrical polyether alkyl polysiloxanes with good oil compatibility and spreading. However, these asymmetrical alkyl polyether siloxanes are uneconomical to use due to difficult and cost intensive manufacturing processes such as those requiring expensive alkyllithium reagents, and they provide only moderate benefits in the spreading of mineral oils.
In 2004, Gaskin et al. reported the used of alkylsilicone adjuvants with a vegetable oil and potash to improve the evenness and efficiency of drying sultana grapes and reported that alkylsilicone adjuvants could reduce surface tension of a vegetable-based drying oil and increase the spreading of an oil emulsion on grapes (see Gaskin et al., Proceeding of the 7th International Symposium on Adjuvants for Agrochemicals (ISAA 2004), 8-12 Nov. 2004 (Cape Town, South Africa) pgs. 24-29).
However, the drying compositions of Gaskin are not suitable for general agrochemical use as the drying compositions required the use of potash which significantly increased the pH of the composition. Moreover, the degree of spreading was dependent on the ratio of potash to oil and the emulsion compositions of Gaskin required that the alkylsilicone adjuvant be mixed with oil prior to emulsification with water. Pesticidal oil compositions or mineral oil-based compositions were not considered in this study.
Nakanishi et al. (US Patent Application Publication 2005/0261133) refers to low molecular weight siloxanes with a low silicon character and hydrophilic glycerol substituents for enhanced oil spreading.
Sieverding et al. (US Patent Application Publication 2005/0244357) refer to a solvent-containing emulsifiable formulation substantially free of water, comprising at least one or more organic solvents, one or more emulsifier and one or more agriculturally acceptable active agents, and a formulation synergist comprising one or more polyether or alkyl modified siloxanes. It was discovered that low molecular weight polyether modified siloxanes without unmodified polydimethylsiloxane units were especially efficient. Siloxanes with high silicone character were not investigated, and no effort was done to find adjuvants which are especially efficient in mineral oil-containing formulations.
Therefore, a need still exists in the art for oil-based, e.g. mineral oil or vegetable oil-based agrochemical compositions which produces a decrease in surface tension and increase in spreading, minimize the amount of oil used while retaining the effectiveness of their agrochemical effects, and maintains an agrochemically acceptable pH.